Using excess 4He to quantify variability in aquitard leakage

W. Payton Gardner, Glenn Harrington, Brian Smerdon

    Research output: Contribution to journalArticlepeer-review

    23 Citations (Scopus)

    Abstract

    Fluid flux through aquitards controls the rate of recharge, discharge, cross-formational fluid flow and contaminant transport in subsurface systems. In this paper, concentrations of 4He are used to investigate the spatial distribution of vertical fluid flux through the regionally extensive Great Artesian Basin aquitard system in northern South Australia. Two vertical profiles of 4He concentration in aquitard pore water, augmented with regional sampling of aquifers above and below the aquitard were used to estimate fluid flux at multiple locations over a large spatial area. 4He concentrations in the shallow aquifer above the Great Artesian Basin range from atmospheric equilibrium to 1000 times enriched over atmosphere. Fluid flux through the aquitard was estimated by fitting observed helium concentrations at each sampling site with a 1-D model of helium transport through the aquitard. Estimated fluid fluxes through the aquitard vary over three orders of magnitude across the study area. In areas of competent aquitard, fluid fluxes are less than 0.003mm/yr, and mass transport of helium is dominated by molecular diffusion. Preferential discharge zones are clearly identifiable with fluid fluxes up to 3mm/yr. Our results show that fluid flux through a regionally extensive aquitard can be highly variable at large spatial scales, and that 4He concentrations in aquifers bounding the aquitard system provide a convenient and sensitive method for investigating aquitard flux at the regional scale.

    Original languageEnglish
    Pages (from-to)63-75
    Number of pages13
    JournalJournal of Hydrology
    Volume468-469
    DOIs
    Publication statusPublished - 25 Oct 2012

    Keywords

    • Arid zone hydrology
    • Environmental tracers
    • Groundwater discharge
    • Noble gas geochemistry

    Fingerprint Dive into the research topics of 'Using excess 4He to quantify variability in aquitard leakage'. Together they form a unique fingerprint.

    Cite this